602 J. E. MAER ON THE PREDEVONIAN 



' Students' Elements ' (p. 485). Speaking of the Menevian beds, he 

 says (from information by Hicks, Q. J. G. S. vol. xxviii. p. 174), 

 " Blind Trilobites are also found, as well as those which have the 

 largest eyes, such as Micro discus on the one hand and Anopolenus on 

 the other." In a lecture on deep-sea fishes delivered at Cambridge 

 by Dr. Giinther, he remarked that these fishes had either very large 

 eyes or none at all, as ordinary eyes would be valueless at such a 

 depth. Sir Wyville Thomson also, in his Voyage of the ' Challenger ' 

 (Atlantic, vol. i. p. 131), points out the resemblance of the eyes of 

 the deep-sea Gystosoma Neptuni to those of ^ghna. We may 

 infer, therefore, that where we meet with a deposit containing Trilo- 

 bites with abnormally large and abnormally small eyes, but not 

 with those of ordinary size, they point to deep-sea conditions. 

 This inference is justified by finding that beds containing such Trilo- 

 bites have generally a fine-grained texture, and exhibit similar 

 lithological characters over large areas. 



The lowest bed of etage D, viz. d 1 a, has been described as con- 

 glomeratic in some places, gritty in others. At Krusna Hora, where 

 it consists of grit, it has yielded abundance of Lingula Feistmanteli, 

 the only fossil as yet known in it. I think this zone represents 

 part of the Lingula Flags of Britain, and is, like them, of a shallow- 

 water origin. Dr. Hicks, in above-cited table, correlates Lingula 

 Mags with conglomerates. 



D d 1 /3 is not very fossiliferous. Besides some Lingulce and Discince, 

 there are recorded from it Harpides Orimmi, AmpTiion Lindaueri, 

 Orthis desiderata, and Echinosphcerites ferrigena. The occurrence of 

 Harpides with Amphion seems to indicate an admixture of primor- 

 dial and later forms. This would agree very well with what we 

 find in the Tremadoc Slates. But the lithological character of the 

 beds is the most remarkable, for the pisolitic ironstones are abso- 

 lutely undistinguishable from those of the Tremadoc Slates of our 

 own area, and, like them, contain much phosphorus. Succeeded as 

 these ironstones are by beds (d 1 y) which have been recognized by 

 many authors as of Arenig age, we can hardly help correlating them 

 with the Tremadoc Slates. 



D d ly has the peculiar flaky and very fine black shales so 

 characteristic of the more typical Arenig rocks of Britain. There 

 are indications of this being a deep-sea deposit, from the eyes of its 

 Trilobites. ^glina is abundant, and, on the other hand, several 

 species of Agnostus occur. Even in the same genus, as pointed out 

 by Herr Dusl, the eyes diifer largely, e. g. in Illcenus, of which J. 

 Katzeri has aborted eyes, and I. advena very large ones. Being a 

 deep-water deposit, we find that the fauna strongly resembles that 

 of the British Arenig rocks, and still more strongly beds of that age 

 in Erance, so that there certainly seems to have been a continuous 

 sea at this period throughout Western Europe. The following 

 genera occur in the Arenig rocks of Britain as well as in d 1 y of 

 Bohemia — jEglina, Placoparia, Oalymene, Trinuclens, Biheiria, 

 Eedonia, Bellerophon. The species of some of these genera strongly 

 resemble one another in the two countries, as pointed out by Mur- 



